1. Field of the Invention
The present invention relates to a method of manufacturing a thin-film magnetic head comprising at least an induction-type magnetic transducer.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as surface recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a recording head having an induction-type magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein the width of top and bottom poles sandwiching the recording gap layer on a side of the air bearing surface is reduced down to microns or the submicron order. Semiconductor process techniques are utilized to implement such a structure.
Reference is now made to FIG. 10A to FIG. 13A and FIG. 10B to FIG. 13B to describe an example of a method of manufacturing a composite thin-film magnetic head as an example of a related-art method of manufacturing a thin-film magnetic head. FIG. 10A to FIG. 13A are cross sections each orthogonal to the air bearing surface of the thin-film magnetic head. FIG. 10B to FIG. 13B are cross sections of a pole portion of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 10A and FIG. 10B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 to 10 xcexcm is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material is formed for making a reproducing head.
Next, on the bottom shield layer 103, alumina, for example, is deposited to a thickness of 100 to 200 nm through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR element 105 for reproduction having a thickness of tens of nanometers is formed. Next, a pair of electrode layers 106 are formed on the bottom shield gap film 104. The electrode layers 106 are electrically connected to the MR element 105.
Next, a top shield gap film 107 as an insulating layer is formed on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 107.
Next, a top shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description) 108 having a thickness of about 3 xcexcm is formed on the top shield gap film 107. The bottom pole layer 108 is made of a magnetic material and used for both a reproducing head and a recording head.
Next, as shown in FIG. 11A and FIG. 11B, on the bottom pole layer 108, a recording gap layer 109 made of an insulating film such as an alumina film whose thickness is 0.2 xcexcm is formed. Next, a portion of the recording gap layer 109 is etched to form a contact hole 109a to make a magnetic path. On the recording gap layer 109 in the pole portion, a top pole tip 110 made of a magnetic material and having a thickness of 0.5 to 1.0 xcexcm is formed for the recording head. At the same time, a magnetic layer 119 made of a magnetic material is formed for making the magnetic path in the contact hole 109a for making the magnetic path.
Next, as shown in FIG. 12A and FIG. 12B, the recording gap layer 109 and the bottom pole layer 108 are etched through ion milling, using the top pole tip 110 as a mask. As shown in FIG. 12B, the structure is called a trim structure wherein the sidewalls of the top pole portion (the top pole tip 110), the recording gap layer 109, and a part of the bottom pole layer 108 are formed vertically in a self-aligned manner.
Next, an insulating layer 111 made of alumina, for example, and having a thickness of about 3 xcexcm is formed on the entire surface. The insulating layer 111 is then polished to the surfaces of the top pole tip 110 and the magnetic layer 119, and flattened.
Next, on the flattened insulating layer 111, a first layer 112 of a thin-film coil is made of copper (Cu), for example, for the induction-type recording head. Next, a photoresist layer 113 is formed into a specific shape on the insulating layer 111 and the first layer 112 of the coil. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer 113. On the photoresist layer 113, a second layer 114 of the thin-film coil is then formed. Next, a photoresist layer 115 is formed into a specific shape on the photoresist layer 113 and the second layer 114 of the coil. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 13A and FIG. 13B, a top pole layer 116 is formed for the recording head on the top pole tip 110, the photoresist layers 113 and 115, and the magnetic layer 119. The top pole layer 116 is made of a magnetic material such as Permalloy. Next, an overcoat layer 117 of alumina, for example, is formed to cover the top pole layer 116. Finally, machine processing of the slider including the foregoing layers is performed to form the air bearing surface 118 of the thin-film magnetic head including the recording head and the reproducing head. The thin-film magnetic head is thus completed.
FIG. 14 is a top view of the thin-film magnetic head shown in FIG. 13A and FIG. 13B, wherein the overcoat layer 117 and the other insulating layers and insulating films are omitted.
In FIG. 13A, xe2x80x98THxe2x80x99 indicates the throat height and xe2x80x98MR-Hxe2x80x99 indicates the MR height. The throat height is the length (height) of portions of the two magnetic pole layers between the air-bearing-surface-side end and the other end, the portions facing each other with the recording gap layer in between. The MR height is the length (height) of the MR element between an end of the MR element located in the air bearing surface and the other end. In FIG. 13B, xe2x80x98P2Wxe2x80x99 indicates the pole width, that is, the recording track width. In addition to the factors such as the throat height and the MR height, the apex angle as indicated with xcex8 in FIG. 13A is one of the factors that determine the performance of a thin-film magnetic head. The apex is a hill-like raised portion of the coil covered with the photoresist layers 113 and 115. The apex angle is the angle formed between the top surface of the insulating layer 111 and the straight line drawn through the edges of the pole-side lateral walls of the apex.
With an increase in recording density of a hard disk drive used for computers and so on, the frequency of data to write or read through the use of a thin-film magnetic head has increased. Thin-film magnetic heads that exhibit an excellent high frequency characteristic are therefore desired.
If the frequency of data to write increases, eddy current loss increases in the magnetic layers making up the magnetic path of an induction-type magnetic transducer. An increase in eddy current loss results in problems such as: a reduction in intensity of a write magnetic field generated from the pole portions opposed to each other with the gap layer in between; an increase in delay between a write current supplied to the coil and generation of a write magnetic field; and a decrease in gradient of rise of a write magnetic field with respect to time. These problems are specifically represented as an increase in nonlinear transition shift (NLTS), for example.
It is therefore preferable that the magnetic layers are made of a high-resistance magnetic material in order to implement a thin-film magnetic head capable of operating in a good condition in a high frequency band.
It is difficult to form a magnetic layer of a high-resistance magnetic material through plating. Therefore, in the prior art, a layer of a high-resistance magnetic material is formed through sputtering, and an etching mask is formed on this layer through photolithography, the mask corresponding to a desired shape of the magnetic layer. The layer is then etched through ion milling, for example, using the mask. The magnetic layer is thus formed.
However, this method of making the magnetic layer has a problem that it takes a long time to etch the layer of the high-resistance magnetic material. Furthermore, ion milling may cause accumulation of electric charge in the stacked layers, and punctures of the very thin shield gap films between the MR element and the shield layers, for example, may be caused by a static discharge.
It is an object of the invention to provide a method of manufacturing a thin-film magnetic head for allowing a magnetic layer of an induction-type magnetic transducer to be formed in a short time without any accumulation of electric charge.
The method of the invention is provided for manufacturing a thin-film magnetic head comprising: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The method includes the steps of: forming the first magnetic layer; forming the gap layer on the first magnetic layer; forming the second magnetic layer on the gap layer; and forming the coil. At least one of the step of forming the first magnetic layer and the step of forming the second magnetic layer includes the step of forming a layer including a yoke portion that faces the coil while the yoke portion is insulated from the coil. The step of forming the layer including the yoke portion includes the steps of forming a frame made of an insulating material around a region where the layer including the yoke portion is to be formed; forming a layer including a magnetic material inside and on top of the frame; and flattening a top surface of the layer including the magnetic material so that the frame is exposed.
According to the method of the invention, the layer including the yoke portion is formed through the flattening process, instead of etching.
According to the method of the invention, the layer including the magnetic material may be made of a high-resistance magnetic material. In the invention the high-resistance magnetic material is a magnetic material whose electrical resistance is 25 xcexcxcexa9-cm or greater.
According to the method of the invention, the layer including the magnetic material may be made of a plurality of layers of a magnetic material and at least one insulating film that are alternately stacked.
According to the method of the invention, the layer including the magnetic material may be formed through sputtering.
According to the method of the invention, the step of flattening may be performed through chemical mechanical polishing.
According to the method of the invention, at least one of the magnetic layers may include: a pole portion layer including one of the pole portions; and a yoke portion layer connected to the pole portion layer and including the yoke portion. In addition, the layer including the yoke portion may be the yoke portion layer. In this case, the at least part of the coil may be located on a side of the pole portion layer in the step of forming the coil. The method may further include the step of forming an insulating layer that covers the at least part of the coil located on the side of the pole portion layer, the insulating layer having a surface that faces the yoke portion layer, the surface being flattened together with a surface of the pole portion layer that faces the yoke portion layer. In this case, the yoke portion layer is formed on the pole portion layer and the insulating layer flattened.
The method may further include the step of forming an alumina film for insulating every neighboring turns of the thin-film coil from each other through low-pressure chemical vapor deposition.
Other and further objects, features and advantages of the invention will appear more fully from the following description.